The present invention relates to a bandwidth correcting system for a television tuner.
A conventional circuit of this type is shown in FIGS. 1 and 2.
In FIG. 1, reference numeral 11 designates a front end section (RF amplifier, local oscillator, etc); 12, a video intermediate frequency amplifier circuit; and 13, a picture quality adjusting circuit, the output of which is applied to a video amplifier circuit (not shown).
An example of the picture quality adjusting circuit 13 is shown in FIG. 2. As the resistance of a variable resistor VR (enclosed by a dotted line) changes, the video signal frequency response characteric varies as indicated in FIG. 3. Accordingly, the picture quality can be made "hard" or "soft" by manually or automatically operating the variable resistor VR.
In the conventional circuit of FIG. 1, the frequency response characteristic of the intermediate frequency amplifier circuit is corrected after video detection has taken place. Therefore, if the audio intermediate frequency is at a high level at the input of the detector, then various signal beats (for instance, a beat at 920 KHz) will occur in the detector.
Accordingly, an object of the present invention is to provide a bandwidth correcting system in which the above-described difficulties accompanying a conventional video intermediate frequency amplifier circuit have been eliminated, wherein, even when the channel is switched or the input level changes, the resultant video signal has a predetermined desired frequency response characteristic.